Phoenix Area Service
AC Capacitor Replacement in the Phoenix Area
Capacitor problems are common during Arizona heat. CTS tests the capacitor, motor, compressor, wiring, and control circuit before replacing parts.
AC capacitor repair and testing
AC capacitors help motors start and run. When a capacitor gets weak, the system may hum, struggle to start, stop cooling, trip breakers, or leave the outdoor unit silent while the indoor fan still runs.
- Outdoor unit humming or not starting
- Fan motor or compressor start issues
- Repeated breaker trips or intermittent cooling
- Electrical testing before replacing parts
- Clear repair guidance before replacement is discussed
Local service
CTS handles urgent AC repair, AC replacement, commercial HVAC, maintenance, water heaters, and related service across the Phoenix area.
480-696-5033
AC capacitor testing and replacement
A failed capacitor can stop the motor or compressor from starting. CTS also checks the motor, compressor, wiring, contactor, and equipment condition.
Phoenix-area HVAC service
CTS works on residential equipment, rooftops, installs, and troubleshooting calls in Arizona conditions.
Serving Phoenix, Mesa, Chandler, Gilbert, Scottsdale, Tempe, Glendale, Surprise, Cave Creek, Queen Creek, Maricopa, and nearby communities.
Capacitor Problems
AC capacitor failure signs
These problems often involve a capacitor, motor, compressor, or electrical startup issue.
Outdoor unit will not start
The thermostat may call for cooling while the outdoor unit stays quiet, hums, or tries to start without running normally.
System starts and stops
Intermittent operation is often tied to electrical problems, heat stress, safety controls, or a weak component that fails under load.
Warm air from vents
If the blower runs but the system is not removing heat, the outdoor unit, compressor circuit, refrigerant circuit, or airflow path needs to be checked.
Capacitor Service Work
AC capacitor and motor parts
Capacitor and motor problems are common causes of no-cooling and outdoor-unit startup failures.
Capacitor replacement
The replacement capacitor needs to match the system requirements, including the correct microfarad and voltage rating.
Motor and start issues
Motor, compressor, contactor, and wiring problems can look similar to a capacitor problem.
Test before replacing
CTS checks the capacitor, meter readings, wiring, motor, and startup circuit before replacing parts.
Capacitor Video
How AC capacitors help motors start and run
This video gives a visual explanation of start capacitors, run capacitors, and why the correct capacitor matters for motors and compressors. Capacitors are electrical parts inside high-voltage HVAC equipment, so testing and replacement need to be handled safely.
Capacitor Failures In Phoenix AZ
HVAC capacitor replacement information
The harsh climate of Phoenix, Arizona can strain HVAC equipment more than other parts of the country. Your air conditioner's capacitor is one of the most common components to fail. CTS Air Conditioning replaces many capacitors throughout Maricopa County, Arizona every year. If you think you have a bad capacitor on your HVAC unit, we can help.
CTS Air Conditioning provides capacitor diagnostics and testing, capacitor replacement, and new AC capacitors when testing shows that is the failed part.
About HVAC Capacitors
What is a capacitor?
Your HVAC system's capacitor usually looks like a small round or oval shaped metallic cylinder. Many air conditioners have two types of capacitors: a start capacitor and a run capacitor. Capacitors are rated in microfarads, which are usually abbreviated uF or MFD. You should always replace a capacitor with one that has the same voltage and microfarad rating.
In a typical residential air conditioning system, the run capacitor is usually the lower microfarad rating and the start capacitor has a higher rating. A capacitor stores electrical energy, and it should be discharged before handling or you could receive an electrical shock.
Serious electrical safety warning
Serious injury or death can occur when working with electricity. Before touching anything inside the cover of your heating and cooling equipment, know exactly what you are doing.
Capacitors can hold a charge even when power to the AC unit is turned off. High-voltage HVAC equipment should be tested and repaired by a qualified technician.
Electrical Component Basics
What an air conditioner capacitor does
Capacitors store electrical energy and release it to the motor they are connected to. Be very cautious handling them because they can store high voltage and maintain their voltage even when the power to the AC unit is turned off. Most motors in an air conditioner need a capacitor to run.
Start Capacitors
How a start capacitor helps a compressor start
Start capacitors are typically used for air conditioner compressors and only to start the compressor. Once the compressor motor reaches 60% to 75% of its full speed, a relay opens to disconnect the start capacitor from the electrical system. It must be disconnected from the circuit or damage to the motor winding can occur.
The single-phase induction motor typically found in HVAC compressors needs extra starting torque to begin operation. The start capacitor accomplishes this by splitting the phase of electricity into a second coil of wire in the motor called the start winding. The start winding gives the motor lots of starting torque when it is engaged. After the motor is spinning fast enough, a relay disengages the start winding and start capacitor from the electrical circuit.
Run Capacitors
How a run capacitor helps the motor operate
Run capacitors are often found on single-phase induction motors used in blower motors, condenser fan motors, and AC compressors. They are used in heat pumps as well as air handlers found in many residential air conditioning systems in the Phoenix area.
The run capacitor charges as the voltage in a given AC cycle increases. When the voltage begins to decrease, the run capacitor releases its energy to the motor. Run capacitors create a phase shift which greatly improves the efficiency of the motor. Run capacitors are designed to dissipate heat, and a start capacitor should never be used in a run capacitor circuit.
Run capacitors greatly improve the efficiency of an HVAC system by improving the power factor. Run capacitors are always in the electrical system during operation and are not disconnected like start capacitors are.
Why Do HVAC Capacitors Fail?
Heat, age, and electrical stress can wear capacitors out
In time, almost everything will break down and stop working simply due to age. HVAC capacitors are no exception. Due to constantly storing and releasing electrical energy, eventually capacitors will wear out and go bad. The extreme heat experienced in Phoenix, Arizona and the Maricopa County area can dramatically shorten the life of an HVAC capacitor.
Higher demand on an HVAC system in conjunction with higher temperatures can overheat components like capacitors and make them fail. When monsoon season starts, power surges caused by electrical storms can also take out your HVAC system's capacitor.
Electrolytic capacitors are especially sensitive to heat. High temperatures can cause electrolyte evaporation. Leakage current through the capacitor will also generate heat due to power loss. Leakage current can happen after long periods of storage as aluminum oxide can start to dissolve in the electrolyte.
When the electrolyte vapor pressure increases, the seal of the capacitor will bulge. This is a telling sign that the capacitor has experienced some type of thermal failure.
Replacing HVAC Capacitors
Signs and testing before replacement
One of the signs that your air conditioner's capacitor is starting to go bad is high current draw. Other signs of a failing capacitor are bulges in the package or an oil leak.
A common symptom of a bad HVAC capacitor is loud humming noises from the AC condensing unit. If the condensing fan needs help starting, it may be a bad capacitor, but it can also be a motor or electrical problem. Never reach into a powered unit.
To test a capacitor, use a capacitance meter. Before disconnecting the capacitor, make notes of which wires are connected to which terminals on the capacitor. The microfarads measured should be within tolerance of the rated value printed on the part. If testing shows that the capacitor is out of range, replacement may be needed.
High-voltage warning
Turn off power, verify power is off, and understand capacitor discharge before touching HVAC electrical parts. If you are unsure, stop and call a professional.
General replacement process
If a capacitor is measuring out of tolerance and may soon fail, it should be replaced with the proper part. The general process includes turning off power to the HVAC unit, opening the access panel, locating and inspecting the capacitor, confirming the capacitance and voltage rating, discharging and disconnecting the capacitor, labeling or photographing the wires, installing the correct replacement, and testing the system after power is restored.
If the AC unit still does not work after replacement, power should be turned back off and the wiring, capacitor rating, motor, contactor, compressor circuit, and related controls need to be checked. A capacitor is common, but it is not the only reason an air conditioner will not start or cool properly.
Related AC Startup Problems
Capacitor symptoms can overlap with other repairs
No-start AC
Fan motor
Breaker trips
Compressor
Capacitor replacement FAQs
Answers about repair, replacement, maintenance, and service.
What are the signs of a bad AC capacitor?
Common signs include an outdoor unit that hums but will not start, a fan that starts slowly or only runs sometimes, warm air from the vents, repeated breaker trips, short cycling, or intermittent cooling. These symptoms can also come from other electrical or motor problems, so testing matters.
What is the difference between a start capacitor and a run capacitor?
A start capacitor helps provide extra starting torque for a motor or compressor and is usually used only during startup. A run capacitor stays in the circuit while the motor runs and helps the motor operate more efficiently.
Why do AC capacitors fail so often in Phoenix?
Phoenix heat, long cooling cycles, repeated startup demand, aging motors, electrical stress, and monsoon-season power issues can all shorten capacitor life.
Can a bad capacitor make the AC blow warm air?
Yes. If a weak capacitor keeps the outdoor fan or compressor from starting correctly, the indoor blower may still move air while the system is not removing heat.
Is AC capacitor replacement a DIY repair?
Capacitors hold electrical charge and sit inside high-voltage equipment. CTS recommends having the system tested and repaired by a qualified technician.
How does CTS test an AC capacitor?
CTS checks the equipment symptoms, inspects the capacitor and wiring, tests the capacitor rating, and also checks related parts such as motors, contactors, controls, compressor circuits, and current draw before recommending replacement.
Will replacing a capacitor fix every no-cooling call?
No. Capacitor failures are common, but motors, controls, wiring, contactors, compressor issues, and airflow problems can cause a similar no-cooling call.
Can a bad capacitor trip the breaker?
It can contribute to startup problems that trip power, but breakers can also trip from motors, compressors, shorts, wiring, contactors, overheating, or other electrical faults.
Should an older system be repaired or replaced?
That depends on age, repair history, equipment condition, and what the diagnostic shows. CTS compares repair cost against replacement options.
Licensed Local HVAC Service
Licensed, Bonded, and Insured
Certified Technical Services, known as CTS Air Conditioning, is a local, veteran owned HVAC and plumbing contractor. The company is licensed, bonded, and insured and has served Phoenix area homes and businesses since 2001.
Licensed for HVAC
HVAC license: ROC 328467. Licensed HVAC service for repair, replacement, and installation work.
Licensed for plumbing
Plumbing license: ROC 341767. Licensed plumbing support for water heater and selected plumbing work.
Experienced HVAC service
Hands-on HVAC repair and installation experience matters on homes, commercial rooftops, package units, and water heater calls.
Technical terms on this page
The links below explain common HVAC terms referenced on this page. Each definition is written to help identify the part, measurement, or system condition.
Air Conditioner | Airflow | Air Handler | Blower Motor | Capacitor | Coil | Compressor | Condenser Fan | Contactor | Cycling | Disconnect | Heat Pump | HVAC | MFD | Refrigerant | Run Capacitor | Short Cycling | Start Capacitor | Thermostat
Call CTS Air Conditioning
CTS handles AC repair, HVAC service, replacement, maintenance, water heaters, and selected plumbing across the Phoenix area.
480-696-5033